188594-16-3Relevant academic research and scientific papers
Formation of non-racemic tricyclic compounds by intramolecular 1,3-dipolar cycloaddition of nitrones
Aurich, Hans Guenter,Geiger, Michael,Gentes, Christian,Koester, Heiner
, p. 841 - 844 (1996)
3-Oxanitrones 10 and 3-azanitrones 11 were prepared starting from (S)-ethyl lactate 5 and (S)-N-benzyl alaninol 8, respectively. Both nitrones underwent spontaneously an intramolecular cycloaddition affording the tricyclic compounds 12 and 13. The diastereomeric forms of 12 and of 13 were separated by column chromatography and identified by NMR spectroscopy.
Formation of enantiopure tricyclic compounds by intramolecular 1,3- dipolar cycloaddition of nitrones
Aurich, Hans Guenter,Geiger, Michael,Gentes, Christian,Harms, Klaus,Koester, Heiner
, p. 3181 - 3196 (2007/10/03)
Nitrones 6 prepared from ester 5 underwent an intramolecular cycloaddition affording diastereomeric mixtures of tricyclic compounds 7A/B. These were separated to give the enantiopure compounds 7A and 7B. Starting from aminoalcohol 8 compounds 10A and 10B were formed via nitrones 9, Nitrone 9a yielded the transproduct 10aC in addition. X-ray analyses confirm the structure of TaB and 10aA. Catalytic hydrogenation of compounds 7A and 7B yielded the bicyclic c-aminoalcohols, which were tested as ligands in the enantioselective addition of diethylzinc to benzaldehyde.
Bicyclic and tricyclic compounds with β-amino alcohol groups as chiral ligands in the enantioselective reaction of diethylzinc with aldehydes
Aurich, Hans Guenter,Biesemeier, Frank,Geiger, Michael,Harms, Klaus
, p. 423 - 434 (2007/10/03)
Reduction of the enantiomerically pure allyloxy esters 9 or ent-9 with DIBAH afforded the corresponding aldehydes which were treated in situ with chiral or achiral hydroxylamines 8 to give nitrones 10. These underwent a spontaneous intramolecular 1,3-dipolar cycloaddition, affording the bicyclic compounds 11 and 12, respectively. In an analogous manner, a mixture of the tricyclic compounds 14 and 15 was prepared. Treatment of compound 16 with cyclohexene oxide afforded a mixture of diastereomers 17 and 18. Diastereomers 14 and 15 as well as 17 and 18 could be separated by chromatography. X-ray analyses of compounds 11Ff, 17, and 11Af · HCI were performed. The bicyclic and tricyclic compounds were used as chiral ligands in the reaction of diethylzinc with aldehydes 19, in particular with benzaldehyde (19a). Using bicyclic compounds with a tertiary β-hydroxyalkyl substituent at the N atom as ligands, ee's in the range of 78 to 95% were found. Whereas for the best ligands 11Ae and Af the enantioselectivity in the reaction of 4-tolualdehyde was only slightly decreased, with the aliphatic aldehydes 19c and d distinctly lower enantioselectivities were determined. VCH Verlagsgesellschaft mbH, 1997.
